Infant resuscitator



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INFANT RESUSCITATOR Filed Nov. 26, 1962 4 SheetsSheet 1 Fig. I

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4 Sheets-Sheet 2 E. W. ROBINSON INFANT RESUSCITATOR Apzrifi 1'11, 395? Filed Nov. 26, 1962 m Ms 3-95? E. w. ROBINSON 3,333,295

INFANT RESUSCITATOR Filed Nov. 26, 1962 4 SheetsSheet 5 fiber! W flab/man I N VENTOR.

United States Patent Ofitice snares Patented Apr. ll, 1S5? 3,313,295 INFANT RESUSCITATGR Elbert W. Robinson, Amarillo, Tex., assignor to The Congregation of the Sisters of Charity of the Incarnate Word, Inn, San Antonio, Tex.

Filed Nov. 26, 1962, Ser. No. 246,035 12 Claims. (Cl. 12830) This invention relates to a novel and useful resuscitator and more specifically to a resuscitator including a pair of sealed chambers for receiving the head and body portion of patients.

The resuscitator of the instant invention includes pump means communicated with each of the chambers and which may be utilized to raise and lower the pressure of the atmospheres disposed in the chambers. The pump means of the resuscitator is not used directly to change the atmosphere in either of the sealed chambers but merely as a means for raising and lowering the pressures of the atmospheres disposed in the chambers inversely relative to each other.

The resuscitator of the instant invention includes means whereby a selected atmosphere may be admitted into the chamber of the resuscitator adapted to receive the head of a pateient and an exhaust valve is provided for auto matically venting the head chamber of the resuscitator to the ambient atmosphere at the end of each cycle of the pump means which increases the pressure within the head chamber. In this manner, from the beginning of the cycle of the pump means for increasing the pressure of the atmosphere disposed in the head chamber, the head chamber atmosphere is increased in pressure. However, at the end of this cycle or just prior to the beginning of the cycle of the pump means utilized to decrease the pressure in the head chamber, the head chamber is vented to the ambient atmosphere whereby the excess pressure therein may be exhausted and thereafter enabling the pump means to reduce the pressure of the atmosphere within the head chamber to a point lower than the pressure of the ambient atmosphere after the venting valve has been closed. In this manner, as long as means is provided for continually admitting a selected atmosphere into the head chamber from a suitable pressurized source the atmosphere within the head chamber will be continually changed.

The main object of this invention is to provide an infant resuscitator which may be utilized to precisely control the condition of the atmosphere provided and forced into and exhausted from the lungs of a patient within the resuscitator.

A further object of this invention, in accordance with the immediately preceding object, is to provide a resuscitator including means by which the pressure differential effected by the pump means in each of the two chambers of the resuscitator may be accurately controlled.

Still another object of this invention is to provide a resuscitator including means whereby the timing of the cycles of increased and decreased pressure within both chambers of the resuscitator may be accurately controlled.

Still another object of this invention is to provide a resuscitator in accordance with the two immediately preceding objects including means by which the pressure differential and the timing of the cycles of increased and decreased pressure effected by the pump means may be varied independently of each other.

Yet another object of this invention is to provide a resuscitator in accordance with the three immediately preceding objects including means by which the timing of the cycling of the pumn means and the pressure differential in the two chambers of the resuscitator effected by the pump means may be independently adjusted during operation of the pump means and without causing any interruption in the function of the resuscitator.

Another object of this invention is to provide an infant resuscitator in accordance with the preceding objects including an actuator for the venting exhaust valve whereby the timing of the opening of the exhaust valve during each of the corresponding cycles of the pump means may be adjusted.

Still another object of this invention, in accordance with the immediately preceding object, is to provide a venting exhaust valve including actuating means whereby the duration of the opening of the exhaust valve may be adjusted independently of the speed of operation of the pump means.

A still further object of this invention, in accordance with the preceding objects, is to provide an infant resuscitator including means defining two separate chambers for receiving the head and body portions of a patient and constructed in a manner whereby free admittance to the body chamber may be gained without interfering with any function of the infant resuscitator in connection with the head chamber thereof.

A final object to be specifically enumerated herein is to provide an infant resuscitator in accordance with the preceding objects which will conform to conventional forms of manufacture, be of simple construction and easy to use so as to provide a device that will be economically feasible, long lasting and relatively trouble free in operation.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a side elevational view of the resuscitator;

FIGURE 2 is an end elevational view of the resuscitator as seen from t .e left side of FIGURE 1;

FIGURE 3 is a fragmentary enlarged longitudinal vertical sectional view of the resuscitator taken substantially upon the plane indicated by the section line 3-3 of FIGURE 2;

FIGURE 4 is a fragmentary end elevational view of the resuscitator similar to that of FIGURE 2 but shown with the head chamber thereof removed;

FIGURE 5 is a fragmentary horizontal sectional view taken substantially upon a plane passing over the motor means of the resuscitator and spaced slightly above the motor means;

FIGURE 6 is a fragmentary enlarged transverse sectional view taken substantially upon a plane disposed immediately forward of the motor means of the resuscitator and looking to the rear end of the resuscitator;

FIGURE 7 is a fragmentary vertical sectional view taken substantially upon the plane indicated by the section line 77 of FIGURE 5;

FIGURE 8 is a fragmentary longitudinal vertical sectional view taken substantially upon the plane indicated by the section line 3-8 of FIGURE 5;

FIGURE 9 is a fragmentary sectional view taken substantially upon a plane passing through the longitudinal center-line of the crank arm of the motor means; and

FIGURE 10 is an exploded perspective view of the removable seal disposed between the head and body chambers of the resuscitator.

Referring now more specifically to the drawings the numeral 16 generally designates the resuscitator of the instant invention. The resuscitator 10 includes a support frame generally referred to by the reference numeral 12 provided with caster wheel assemblies 14 whereby the frame 12 may be readily moved from one location to another.

The resuscitator includes a housing generally referred to by the reference numeral 16 and it may be seen that the housing 16 comprises a cylindrical body portion 18 and a cylindrical head portion or section 20. Each of the portions or sections 18 and 26 defines a compartment and it will be noted that the compartment defined by the body portion 13 is larger than the compartment formed by the body portion 29. The body portion 18 is adapted to receive the body of a person while the head section or portion 20 is adapted to receive the head of a persons body.

The head section 20 is pivotally secured to the body section 18 by means of a pair of hinges 22 and 24 and it may be seen that the confronting ends of the body and head sections 18 and 2% are provided with annular flanges 26 and 28. The flange 28 carries an annular sealing ring 30 for forming a fluid-tight seal between the flanges 26 and 23.

An opening 32 is formed in the end wall 34 of the body section 18 and an annular mounting plate 36 is pivotally secured to the end wall 34 by means of a suitable pivot 38 which is secured through the opening 40 formed in the mounting plate 36. The mounting plate 36 includes a slotted car 42 whereby the annular mounting plate 36 may be secured in registry with the opening 32 by means of the fastener 44, see FIGURE 4.

The mounting plate 36 includes a semi-circular seal member 46 and a removable semi-circular seal member 48 including a handle 50 is provided for insertion be hind the mounting plate 36 prior to the securement of the mounting plate 36 in position in registry with the opening 32. In this manner, the semi-circular seal members 46 and 48 may snugly embrace the neck of the patient 52 disposed within the resuscitator 10.

The body and head sections 18 and 20 may be provided with suitable windows 54 and 56 respectively and it may further be seen from FIGURES 1 and 3 of the drawings that the rear end of the body section 18 is provided with a hinged end wall 58 including an annular seal 60 which may be swung into and out of positions closing the rear end of the body section 18. A suitable latch 62 is provided for securing the end wall 58 in its closed position.

A body supporting tray 62 is slidingly supported in the body section 18 by means of suitable guideways 64 disposed on opposite sides of the body section 18 and the tray 62 has a contour foam rubber supporting pad 66 disposed therein.

A head basket 68 is supported in the head section 20 and has a contoured head pad 70 disposed therein. Accordingly, it may be seen that the body of the patient 52 may be comfortably supported by the pad 66 while the head of the patient 52 may be comfortably supported by the pad 7%.

Suitable pressure gages 74 and 76 are mounted on the body and head sections 18 and 20 and are communicated with the interiors thereof for indicating the pressure of the atmospheres disposed therein. A thermostat 78 is supported from and projects into the body section 18.

Supported from the frame 12 are three bellows members 80, 82 and 84. The bellows members 82 and 84 are mounted in a side-by-side relation and have corresponding ends secured to and in communication with the interior of the brace 86 while the bellows member 80 has one end secured to the brace 88 and communicated with the inlet end of a flexible conduit 90. A connecting assembly generally referred to by the reference numeral 92 connects the ends of the bellows members 82 and 84 remote from the brace 86 and the end of the bellows member 80 remote from the brace 88 together. One end of an oscillatory or reciprocable actuator arm assembly 94 is pivotally secured to the connecting assembly 92 while the other end of the arm assembly 94 is pivotally secured to the frame 12 as at 96. Accordingly, upon oscillatory movement of the arm assembly 94,

4: the bellows member 86 and the bellows members 82 and 84 will be alternately collapsed and extended.

The flexible conduit has its discharge end communicated with an inlet opening 96 formed in the lower end of the head section 29 tnd the hollow brace 86 is communicated with the interior of the body section 18 at its upper end.

An outlet opening 100 is formed in the bottom of the head section 20 and a solenoid actuated exhaust and venting valve assembly generally referred to by the reference numeral 162 controls the outlet opening 109.

A suitable supporting rack 104 is supported on the front wall 106 of the head section 20 and is vertically adjustable thereon by means of the pin and slot connections 1G8 and 110.

Any suitable type of pressurized container or nebulizer 112 containing the desired atmosphere may be supported from the support rack 104. The pressurized container 112 includes an outlet neck 114 which is controlled by a valve assembly generally referred to by the reference numeral 116 whereby the atmosphere within the pressurized container 112 may be admitted into the head section 20 by means of the inlet opening 118.

The body section 18 includes a suitable latch 120 for securing the head section 20 in the closed position and a suitable electric heater such as a Calrod 122 may be provided and controlled by the thermostat 78 for warming the atmosphere within the body section 18.

With attention now directed more specifically to FIG- URES 5 through 9 of the drawings, it may be seen that the actuator arm 94 for the pump means which includes the bellows S0, 82 and 84 has one end of a connecting rod 126 pivotally secured thereto, the other end of the adjustable connecting rod 126 is pivotally secured to a crank arm 128 as at 130 and it may be seen that the crank arm 128 includes a longitudinal keyway 132 in which a slide member 134 is shiftable. A screw member 136 including a diametrically enlarged head 138 is rotatably supported on the crank arm 128 by means of journal block 149 and the slide member 134 with which the screw member 136 is threadedly engaged. The slide member 134 includes a spindle portion 142 to which the adjacent end of the connecting rod 126 is pivotally secured by means of a suitable fastener 144 which includes a shank portion (not shown) that is threadedly engaged in the blind bore 146 formed in the spindle portion 142. Accordingly, upon rotation of the screw member 136, the effective length of the crank arm 128 may be varied.

As can best be seen from FIGURE 6 of the drawings a control rod 150 having a knob 1'60 on its outer end is mounted from the frame 12 for longitudinal reciprocation and has a pair of abutment plates 152 and 154 mounted thereon at points spaced longitudinally there along. A pair of expansion springs 156 are secured between the frame 12 and the plates 152 and 154 and normally yieldingly urge the plates 152 and 154 toward positions in which each is slightly spaced from the circular path of movement of the diametrically enlarged head portion 138 formed on the end of the screw member 136 remote from the slide member 134. From FIGURE 7 of the drawings it will be noted that each of the abutment plates 152 and 154 are substantially arcuate in plane and include portions which are registered with portions of the circular path of movement of the head portion 138.

The crank arm 128 is mounted on the output shaft 161 of a reduction gearing assembly generally referred to by the reference numeral 162 which is supported from the frame 12. The reduction gearing assembly 162 includes an input shaft 164 on which a pulley generally referred to by the reference numeral 166 is mounted. The pulley includes a flange 168 which is fixed on the shaft 164 and a flange 170 which is shitfable axially on the shaft 164. A compression spring 172 normally yieldingly urges the flange 170 toward the flange 168.

An electric motor generally referred to by the reference numeral 174 is supported from the frame 12 and includes an output shaft 176 on which a pulley generally referred to by the reference numeral 178 is mounted. The pulley 478 includes a pulley flange 18% which is fixed relative to the shaft 175 and a pulley flange 182 which is shiftable axially of the shaft 176.

The frame 12 includes a stand 134 with which an adjusting screw shaft 186 is tlrreadedly engaged. The adjusting screw shaft 186 includes an actuating knob 188 on its outer end and the inner end of the adjusting screw shaft 186 includes a rotatable connection with the flange 182 that will enable axial thrust on the flange 132 to be effected by the adjusting screw shaft 186.

An annular cam carrier disk 19%) is mounted on the output shaft 161 and is fixed in adjusted rotated positions thereon by means of a pair of setscrews 192. A cam member 194 is fixed on the cam carrying disk $190 by means of suitable fasteners 21% and may be adjusted radially of the cam carrying disk 19%; by means of slots (not shown) formed in the cam member 1%. The cam member 194 includes an arcuate cam surface 198 which has a radius of curvature less than the distance from the cam surface 1% to the center of the output shaft 1:39. A normally closed microswitch assembly generally referred to by the reference numeral is provided and is utilized to close an electrical circuit (not shown) for actuating the electric solenoid controlled vent valve assembly 1 32 which is normally gravity-urged to an open position.

In operation, the rear or end wall 53 is first opened and then the head section is swung to the full open position. The head basket ea and cushion or pad are then properly positioned as shown in FIGURE 3 of the drawings. The semi-circular seal member 48 is then removed and the body tray :52 may be moved to its fully extended position with a major portion thereof projecting re viardly through the open rear end of the body section 13. The patient 52 may then be placed in the body tray 62 and the tray 62 may then be slid back into the position within the body section 18 illustrated in FIGURE 3 of the drawings. As the body tray 62 is moved to the position illustrated in FlGURE 3 of the drawings, the head of the patient 52 is guided carefully through the opening 32 and positioned in a manner such that the neck of the patient 52 is properly cradled by the semi-circular seal member 46 and its head is correctly supported by the padding or cushion 7G. Thereafter, the semi-circular seal member 48 may be properly secured in position as lustrated in FIGURE 3 of the drawings in order that the seal member 43 and the seal member 45 may snugly e=mbrace the neck of the patient 52. At this point, the electric motor 174 may be started and the adjusting screw member 186 may be manipulated in order that the motor 174 will effect the proper number of cycles of operation of the pump means in a given period of time. Then, the end wall 58 and head section 23 may be secured in the closed positions illustrated in FIGURE 3 of the drawings. Thereafter, the pressure gages '74 and '76 may be observed and the shaft 151'} may be manipulated by means of the knob 16% in order to properly position the shank portion or spindle 142 to obtain the desired amount of pressure differential in the body and head sections 18 and 2d.

The heater elements 122 may then be actuated if desired and the nebulizer 112 is actuated to provide the desired rate of change of the atmosphere within the head section 29.

If it is desired to increase the pressure differential in the body and head sections 18 and 20, the screw member 136 may be adjusted by means of the abutment plates 152 and 154. Additionally, the rate of cycling of the pump means may be adjusted by means of the adjusting screw shaft 186 and the timing of the opening of the vent valve assembly 162 may be adjusted by loosening the setscrews 6 192 and rotating the disk 1% relative to the shaft 168. Still further, the cam member 194- may be adjusted radially of the disk 199 in order that the duration of the operation of the vent valve assembly 102 may be varied independently of the speed of operation of the pump means.

Petcocks 2-81 and 292 are provided on each of the body and head sections 18 and 20 to provide fine adjustment of the pressure differential of the atmospheres within the sections 18 and 20 and to provide makeup air for the pump means if desired. In addition, taps 204 and 266 may be provided for electrocardiogram wiring and openings 208 and 216 may be provided to enable intravenous feeding to be carried out. Still further, openings 212 and 214 are provided whereby vacuum pump tubing may be utilized for the removal of liquids and a closable open- 2l6 is provided in the end Wall 136 for the insertion of an atomizer discharge tube.

It is to be noted that the head basket 68 is supported from the end wall 34 of the body section 18 thereby enabling the head section 2 9 to be pivoted to the open position durin operation of the resuscitator whereby the increase and decrease of pressure about the body of the patient 52 will be suificient to maintain the patients breathing. Additionally, the end wall 58, when the head section as is in the closed position, may be opened providing access to the interior of the body section 18 without interrupting the breathing of the patient 52 which is then maintained by means of the head section 26.

Although the bellows 82 and merely increase and decrease the pressure of the atmosphere Within the body section 18, the pressure of the atmosphere within the head section 2% is raised to a point above normal atmospheric pressure until the vent valve assembly Till opens and reduces the pressure within the head section 24 to substantially that of normal atmospheric pressure. Then, after the vent valve assembly Till closes, the bellows 5i) reduces the pressure within the head section 24 to a point below the pressure of the ambient atmosphere. Thus, it may be seen that the conditioned atmosphere being discharged from the pressurized container 112 may be precisely controlled.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling Within the scope of the invention as claimed.

What is claimed as new is as follows:

1. An infant resuscitator com-prising a housing including a pair of closed adjacent compartments adapted to receive a person or animal with his head disposed in a first compartment of said housing and his body in a second compartment of said housing, said housing including means adapted to form a seal about the neck of a person extending between said compartments, air pump eans including first and second variable volume closed pumping chamber means communicated with the interiors of said first and second compartments respectively, and operable to alternately increase and decrease the pressure of the atmosphere in said chambers with said chambers being simultaneously pumped inversely relative to each other, said first compartment including exhaust value means communicated directly with the interior of said first compartment and operable in response to operation of said pump means for intermittently venting said first compartment, said first and second closed pumping chamber means being directly communicated with said first and second compartments independent of any air flow controlling valve means, said exhaust valve means including actuating means therefor connected with said air pump means and operable to intermittently open said exhaust valve means near the periods of minimum volume of said first closed pumping chamber means independent of the diiferential in pressure between the air pressure of the ambient atmosphere and the air pressure in said first compartment to the ambient atmosphere near the ends of periods of increased atmospheric pressure in said first compartment, and means for admitting a selected atmosphere into said first compartment.

2. The combination of claim 1 wherein said pump means include means for varying said quantity of pumped atmosphere during operation of said pump means and independently of the cycling speed of said pump means.

3. The combination of claim 1 including motor means, means drivingly connecting said motor means to said pump means and including means for varying the cycling speed of said pump means relative to said motor means while maintaining constant driving connection between said motor means and said pump means.

4. The combination of claim 3, said pump means including means for varying said quantity of pumped atmosphere during operation of said pump means and independently of the cycling speed of said pump means.

5. The combination of claim 4, said exhaust valve actuating means including means which may be adjusted to vary the duration of the opening of the exhaust valve means independently of the cycling speed of said pump means.

6. The combination of claim 1 wherein said exhaust valve actuating means includes means which may be adjusted to advance and retard the time of actuation of said exhaust valve means relative to a given cycle of operation of said pump means.

7. The combination of claim 6, said actuating means also including means which may be adjusted to vary the duration of the opening of the exhaust valve means independently of the cycling speed of said pump means.

8. An infant resuscitator comprising a closed housing compartment adapted to receive the head of a person or animal and including means adapted to form a seal about the neck of said person, air pump means communicated with the interior of said compartment and including a substantially closed pumping chamber and operable to alternately increase and decrease the pressure of the atmosphere in said compartment, said compartment including exhaust valve means operable in response to operation of said pump for alternately venting said compartment to the ambient atmosphere near the ends of periods of increased atmospheric pressure in said compartment, and means for emitting a selected atmosphere into said compartment, said pump means includes a reciprocable actuating member and drive means therefor comprising a rotatable shaft including a crank arm, a connecting rod having one end pivotally secured to said actuating member and means pivotally securing the other end of said connecting rod to the free end of said crank arm and including means for shifting the pivot of said connecting rod to said crank arm longitudinally of said crank arm, said last mentioned means including an adjusting screw for shifting said pivot supported for rotation with its longitudinal axis extending generally radially of said drive means shaft and having an enlarged head portion projecting outwardly from opposite sides of said crank arm at a. point spaced outwardly of the circle scribed by said pivot, abutment means carried by said resuscitator and disposed on opposite sides of the plane through which said crank arm is swingable and selectively shiftable axially of said drive means shaft for engagement with said head portion to rotate the latter during rotation of said drive means shaft, said exhaust valve means including a movable actuator, said drive means also including abutment means intermittently engageable with said actuator for actuation thereof in timed sequence with and in direct response to operation of said drive means.

9. The combination of claim 8, wherein said pump means includes a rotatable input shaft on which an input pulley is mounted, motor means for said pump means including a rotatable input shaft having an output pulley mounted thereon aligned with said input pulley, each of said pulleys including a first pulley flange fixed relative to the corresponding shaft and a movable pulley shiftable axially of the corresponding shaft, means yieldingly urging one of said shiftable flanges toward the corresponding fixed pulley and control means fixed relative to said mounting means and including a movable actuator for positively shifting the other of said pulley flanges y of the corresponding shaft, and an endless flexible me-nber entrained over said pulleys drivingly connecting said output pulley to said input pulley.

i=3. The combination of claim 9 wherein said exhaust valve includes actuating means which may be adjusted to advance and retard the time of actuation of said exhaust valve means relative to a given cycle of Operation of said pump means.

it. The combination of claim 16, said actuating means also including means which may be adjusted to vary the duration of the opening of the exhaust valve means independently of the cycling speed of said pump means.

12. An infant resuscitator comprising a closed housing compartment adapted to receive the head of a person or animal and including means adapted to form a fluid-tight seal about the neck of said person, air pump means communicated with the interior of said compartment including a substantially closed variable volume pumping chamber and operable to alternately increase and decrease the pressure of the atmosphere in said compartment, said compartment including exhaust valve means communicated directly with the interior of said compartment and operable in response to operation of said pump means for intermittently venting said compartment to the ambient atmosphere near the ends of periods of increased atmospheric pressure in said compartment, and means for admitting a selected atmosphere into said compartment, said closed pumping chamber means being directly communicated with the interior of said compartment independent of any air flow controlling valve means, said exhaust valve means including actuating means therefor connected Withsaid air pump means and operative to intermittently open said exhaust valve means near the periods of minimum volume of said pumping chamber means independent of the differential in pressure between the air pressure of the ambient atmosphere and the air pressure in said compartment wherein said exhaust valve includes actuating means which may be adjusted to vary the duration of the opening of the exhaust valve means independently of the cycling speed of said pump means.

References Cited by the Examiner UNITED STATES PATENTS 1,099,473 6/1914 Sundh 103-38 1,898,652 2/1933 Williams 74-600 2,263,844- 11/1941 Hammond 128-30 2,398,520 4/1946 Clements 128-30 2,494,712 1/1950 Leyenaar 12830 2,762,200 9/1956 Huxley 60-62.5 2,770,232 11/1956 Falk 128-29 2,810,384 10/1957 Bloxsom 128-28 3,225,758 12/1965 Morch 128-29 RECHARD A. GAUDET, Primary Examiner.

C. F. ROSENBAUM, Assistant Examiner, 

12. AN INFANT RESUSCITATOR COMPRISING A CLOSED HOUSING COMPARTMENT ADAPTED TO RECEIVE THE HEAD OF A PERSON OR ANIMAL AND INCLUDING MEANS ADAPTED TO FORM A FLUID-TIGHT SEAL ABOUT THE NECK OF SAID PERSON, AIR PUMP MEANS COMMUCIATED WITH THE INTERIOR OF SAID COMPARTMENT INCLUDING A SUBSTANTIALLY CLOSED VARIABLE VOLUME PUMPING CHAMBER AND OPERABLE TO ALTERNATELY INCREASE AND DECREASE THE PRESSURE OF THE ATMOSPHERE IN SAID COMPARTMENT, SAID COMPARTMENT INCLUDING EXHAUST VALVE MEANS COMMUNICATED DIRECTLY WITH THE INTERIOR OF SAID COMPARTMENT AND OPERABLE IN RESPONSE TO OPERATION OF SAID PUMP MEANS FOR INTERMITTENTLY VENTING SAID COMPARTMENT TO THE AMBIENT ATMOSPHERE NEAR THE ENDS OF PERIODS OF INCREASED ATMOSPHERIC PRESSURE IN SAID COMPARTMENT, AND MEANS FOR ADMITTING A SELECTED ATMOSPHERE INTO SAID COMPARTMENT, SAID CLOSED PUMPING CHAMBER MEANS BEING DIRECTLY COMMUNICATED WITH THE INTERIOR OF SAID COMPARTMENT INDEPENDENT OF ANY AIR FLOW CONTROLLING VALVE MEANS, SAID EXHAUST VALVE MEANS INCLUDING ACTUATING MEANS THEREFOR CONNECTED WITH SAID AIR PUMP MEANS AND OPERATIVE TO INTERMITTENTLY OPEN SAID EXHAUST VALVE MEANS NEAR THE PERIODS OF MINIMUM VOLUME OF SAID PUMPING CHAMBER MEANS INDEPENDENT OF THE DIFFERENTIAL IN PRESSURE BETWEEN THE AIR PRESSURE OF THE AMBIENT ATMOSPHERE AND THE AIR PRESSURE IN SAID COMPARTMENT WHEREIN SAID EXHAUST VALVE INCLUDES ACTUATING MEANS WHICH MAY BE ADJUSTED TO VARY THE DURATION OF THE OPENING OF THE EXHAUST VALVE MEANS INDEPENDENTLY OF THE CYCLING SPEED OF SAID PUMP MEANS. 